The present invention is directed to a tie rod secured in an anchorage by at least one of an organic and inorganic mortar composition. The tie rod is formed of a shaft, inserted into the anchorage, having a connecting section and an anchoring section with conically shaped members on the anchoring section.
Aside from classical fastening techniques where the attachments are formed by expansion anchors or undercut systems anchored positively or non positively in a borehole, chemical fastening techniques are also known in the state of the art where a tie rod is inserted into a borehole filled with a mortar composition and is fixed after the mortar composition has hardened or cured. Such composite anchoring systems have the advantage that they are largely free of expanding pressure and, therefore, permit smaller axial and edge distances in the anchorage. For fastening heavy loads, composite anchoring systems are known in which a multi-component organic and/or inorganic mortar composition is filled in a previously prepared borehole. Initially, the components of the mortar composition are maintained separate from one another in glass or plastic containers. A tie rod, as disclosed in EP-B-0 356 425, is driven into the borehole and at the same time, rotates about its longitudinal axis. As it is introduced, the tie rod destroys the containers holding the components of the mortar composition. By rotating the tie rod, the mortar composition is mixed more or less intimately and the shattered container is further comminuted.
Composite anchoring systems are also known where the mortar composition is premixed outside the borehole and then introduced into it. Such composite anchoring systems, which are sold by the assignee, are used predominately for fastenings in brick walls, especially formed of hollow chamber bricks. The mortar composition, usually comprising two reactive components, is discharged by an expelling device from individual containers holding the reactive components and mixed in a device located upstream of the outlet opening of the device and injected into a borehole prepared in the brick wall. To improve the distribution of the already premixed mortar composition and to prevent the mortar composition from flowing away into a chamber in the brick containing the borehole, usually the borehole is equipped with a sleeve provided with openings. To insure that the sleeve equipped borehole is filled completely, the mortar composition is injected in an prescribed filling procedure from the bottom or base to the top. Next, a tie rod is inserted into the borehole containing the injected mortar. After the curing of the injected mortar, the tie rod is fixed in the borehole. Recently, injected mortar has been used to an increasing extent for anchorage in solid materials, such as concrete, rock and wood.
Where the anchorage is formed in a broken base material, in moist boreholes, or boreholes from which the drilled material has been only inadequately removed, anchorages of the tie rod with organic and/or inorganic composite mortars or with injection mortars have an inferior load shifting behavior. In EP-B-0 356 425 an organic composite mortar is supplied in glass cartridges and the tie rods have several consecutively arranged cones in the anchoring section formed from the shaft of the tie rod. During axial displacement of the tie rod under tensile load, the cones, arranged consecutively, are intended to afford a post spreading in the borehole. In the case of known tie rods with multiple cones, the load is introduced into the base material of the anchorage by spreading pressure, which the cones exert under tensile load over the mortar composition in the anchoring base. In broken concrete, it may happen that the load is introduced very unevenly, plus the cones, closer to the anchoring surface, exert a greater spreading pressure than the cones located further inwardly. In such an anchorage, in the case of tensile loads, there is the danger that the concrete spalls in the region close to the anchorage surface, and the load carrying capability of the concrete is only incompletely used.
Therefore, a primary object of the present invention is to eliminate such disadvantages of tie rods in the state of the art. A tie rod is provided which enables loads to be introduced more uniformly into the anchorage base, whereby the load carrying capability of the concrete is better utilized. At the same time, the tie rods are of a simple form and inexpensive to manufacture.
The object of the present invention is to provide a tie rod with conically shaped members on the leading end of the tie rod shaft. Preferred variations and/or advantages for the developments of the tie rod are set forth in the dependent claims. The present invention is intended for anchorages where the tie rod is secured with organic and/or inorganic mortar compositions and has a shaft with a connecting section at one end and an anchoring section at the other. The anchoring section has at least two conically shaped members disposed consecutively in the axial direction and the diameter of such members increases in the direction toward the first or leading end of the tie rod shaft. The conically shaped members are formed of a first end cone secured on the shaft so that it cannot be displaced or shifted axially. A second cone follows the first end cone and is a separate member which can be slipped onto the anchoring section and displaced to a limited axial extent along the anchoring section.
In accordance with the present invention, the tie rod affords a better introduction of the load. In tie rods known in the state of the art, with a number of conically shaped members, formed from the shaft and disposed consecutively in the axial direction, the load is usually distributed from the region close to the surface of the anchorage to the bottom of the borehole. On the contrary, the tie rod in accordance with the present invention affords a very opposite distribution. The axially fixed first end cone, in combination with at least one and preferably several additional cones, which are axially displaceable, insures that the load is always introduced starting from the base of the borehole. As a function of their axial displacability, the load is also distributed over the remaining cones. Overall, a controllable and more uniform distribution of the load from the cones over the mortar into the anchorage base results.
At times it may be necessary to insert the tie rod with the cones in a specific orientation into the borehole. To retain the orientation in the anchored state, the cones are secured against twisting relative to the anchoring section. Twisting is prevented by a positive connection between the tie rods and the cones. In a preferred embodiment of the invention, the anchoring section has a cross section deviating from the circular to achieve this purpose and preferably the cross section is polygonal.
To maintain the diameter of the borehole so that it is not excessively large in relation to the connecting section diameter of the tie rod, the anchoring section, carrying the cones, has a diameter smaller than the diameter of a transition region between the connecting section and the anchoring section. The transition section between the smaller diameter section and the connecting section has the diameter of the tie rod blank. Preferably, the ratio of the outside diameter of the transition section to that of the reduced diameter anchoring section is in a range of about 1.2 to about 1.35. The first end cone at the front of the anchoring section, can be a separate part as are the axially displaceable cones. The first end cone can be slipped or screwed onto the tie rod and then connected to it, so that it cannot be shifted axially. For example, the first end cone can be connected to the shaft by a positive connection, such as riveting, swaging or by threading, or by a connection, such as welding, soldering, gluing and the like. In one embodiment of the invention, advantageous from a manufacturing point of view, the first end cone is constructed as one piece with the anchoring section. In this arrangement, the remaining axially displaceable cones are slipped onto the shaft and the first end cone is integrally molded onto the leading end of the shaft, for example, by swaging, radial riveting and the like.
Where separate cones are provided, which can be slipped onto the anchoring section of the tie rod, there is the possibility of constructing the cones from a material different from the shaft. This affords the opportunity of using different manufacturing processes for the shaft and for the cones. If different materials are selected for the shaft and the cones, it is possible that the tie rod be formed of a stainless steel while the cones are produced from a more easily moldable steel. Moreover, the cones need not all consist of the same material. In its anchoring section, the tie rod may have cones of different materials to achieve loads of different magnitudes at different depths in the borehole and so that the load introduction is adapted, for example, to an anchoring base which is very inhomogeneous over its depth.
In connection with an introduction of the load adapted to the anchorage base, it is advantageous if the tie rod is equipped in the anchoring section with cones having different external diameters and/or cone angles
The axial passage of forces developed during a tensile load from one cone to the next can be influenced by axially cushioned or axially elastic intermediate elements, which can be slipped on the anchoring section of the tie rod between the cones. As an example, a larger load can be assigned over the targeted distribution forces to the cones located in the depth of the borehole, in order to make better utilization of the load carrying capability of the concrete forming the anchorage. The intermediate elements can be metallic elements in the form of discs or springs, such as spring washers. In a preferred embodiment of the invention, the intermediate elements are elastic, plastic disks. The passage of the force can be controlled by the selection of the plastic, the modulus of elasticity and the thickness of the plastic disks. The load is passed on less and later if the modulus of elasticity is lower and/or the thickness of the plastic disks is larger. Instead of plastic disks of different thickness, and it is possible to vary the number of plastic disks disposed between the cones.
The number of cones arranged along the anchoring section which can be shifted axially, depends on the length of the anchoring section. The arrangement of cones along about xc2xd to about ⅔ the length of the anchoring section of the tie rod has proven to be advantageous. In principle, there is no upper limit to the number of cones disposed along the anchoring section. On the basis of manufacturing considerations, however, it has proven to be advantageous that the number of cones including the first end cone, does not exceed 10.
To prevent the tie rod from rotating in the hole when a component part is connected and fastened to it, at least some of the cones may be provided on their radially outer periphery with one or more flat surfaces. The flat surfaces make it easier to insert the tie rod into the borehole filled with the mortar composition. The mortar composition can flow at the flat surfaces and the tie rod is better embedded in the mortar.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by it use, references should be had to the drawings and description matter in which there are illustrated and described preferred embodiments of the invention.